Corrosion resistant aerosol package containing hydrolyzable material



CORROSION RESISTANT AEROSOL PACKAGE CONTAINING HYDROLYZABLE MATERIAL Richard L. Riley, Laurel, Md., assignor to Chempel Inc., Camden, N ..l., a corporation of New Jersey No Drawing. Filed Nov. 13, 1956, Ser. No. 621,506

10 Claims. (Cl. 206-.6)

This is a continuation-in-part of my application Serial No. 562,953, filed February 1, 1956, now abandoned.

This invention relates to chemical compositions under pressure which contain propellants for discharging them from a container through a dispensing valve into the atmosphere.

Since the advent of the so-called aerosol bomb devised by Goodhue and Sullivan (see US. Patent No. 2,321,023), many attempts have been made to find substitutes in whole or in part for the expensive Freons employed as the propellant. The use of Freon alone has the important advantage that the pressure in the container remains substantially constant as the liquid is discharged, thereby giving substantially uniform conditions of dispensing. The Freon is also important as the boiling solvent of the composition and hence cannot be dispensed with entirely in cases where the compositions to be dispensed are to assume a particle size smaller than what can be provided by a wet spray, because the violent boiling of the Freon upon escape to the atmosphere is depended upon to break up the sprayed droplets into even smaller particles. For this purpose, however, it is not necessary, or at least not always necessary, to use large quantities of the Freon, such as in the case when Freon is used as the sole propellant. As a result, constant efforts have been made to find a substitute for at least a portion of the Freon and one such effort has resulted in the use of carbon dioxide.

Accordingly, carbon dioxide has been used in some cases in combination with Freon as a propellant assistant. This, in accordance with the prior art, is done by either charging the container with carbon dioxide gas directly or by the insertion of pellets of solid carbon dioxide (Dry Ice) in the container just before the containers with the usual dispensing valve are hermetically sealed. The solid carbon dioxide soon sublimes into its gaseous form, a portion of which may become dissolved in the liquid phase of the composition.

One of the objects of this invention is the provision of a novel method of providing carbon dioxide gas as a propellant assistant for Freon in compositions of the type mentioned.

A further object of the invention is the provision of a composition of matter adapted to be stored under pressure in a hermetically sealed container.

A still further object of the invention is the reduction in the cost of providing compositions of matter containing propellant gases.

A further object of the invention is to provide aerosol compositions in which water is substituted for a substantial portion of organic solvents previously employed. The cost of manufacturing the composition is accordingly substantially reduced. The nature of the compositions provided by this invention are such that water may be employed as a component along with components such as 2,964,165 Patented Dec. 13, 1960 ice 'propellant assistant aids, in some cases, in making it feasible to reduce the amount of fluorinated hydrocarbon (Freon, lsotron, Genetron) which is also employed as a propellant, and thereby in effecting additional savings in the cost of manufacturing the compositions.

A further purpose of the invention is to provide noncorrosive aerosol compositions employing a substantial proportion of water in which carbon dioxide is employed as a propellant assistant, and which are capable of maintaining the spraying pressure throughout the shelf-life of the composition which at a minimum is from 15 to 20 months.

A further object of the invention is to provide aerosol compositions which comprise an aqueous phase and an organic liquid phase which have substantially similar densities, so that emulsification of the entire composition can be readily attained.

A further object is to provide such compositions which are noncorrosive with respect to tin lined metal containers and in which substantial amounts of carbon dioxide may be dissolved to serve as a propellant assistant.

A further important object of the present invention is to provide aerosol compositions which contain a substantial amount of water and methylene chloride, Freon-l1 or other organic components which are known on hydrolysis to produce corrosive products and which nevertheless are noncorrosive with respect to tin lined metal containers.

It is also an object of the present invention to provide aerosol compositions which employ substantial amounts of water and also alcohols which in past practice have been avoided in compositions comprising water because of the resulting corrosive action on metal containers.

All of these foregoing objects are accomplished in the compositions which are described hereafter in the specific examples.

The term propellant as used herein without any further designation is to be construed as meaning one or more of the low boiling point fiuorochlorohydrocarbons which are commonly employed as aerosol propellants. The term propellant also includes mixtures of these hydrocarbons as well as other commonly known aerosol propellants such as methyl chlorlde, etc. It will also be understood that the propellant will cover mixtures of the compounds mentioned above with vapor pressure modifying components such as methylene chloride, methyl chloroform and similar blends of compounds which are known in the art. The term propellant assistant is meant to designate gases such as carbon dioxide and nitrous oxide which are not condensible at pressures and temperatures ordinarily encountered in aerosol products. Among the fiuorochlorohydrocarbons such as contemplated by the above definition of propellants are the compounds sold generally under the trade designations of Freons, Genetrons and Isotrons. Most commercial aerosol products employ propellants which at room temperature have a vapor pressure of 40 to pounds 7 per square inch and the present invention is accordingly concerned in large degree with propellants exhibiting vapor pressures in this range.

In accordance with one form of the present invention, a portion of the Freon is substituted by an unreacted used, may thus be furnished from an external source as a gas or as a solid, or may be formed in situ, as described above. The presence of the substantial amount of water in the composition enables a tiseful amount of carbon mixture of water, sodium and/ or potassiumbicarbonate v 5 dioxide to be dissolved and therefore permits replaceand an acidjwhich canreact withrthe bicarbonate generate carbon dioxide; The preferred procedure is gto 7 place in. an open container, equipped with the usu discharge or dispensing valve, a quantity of the. material ment of the more expensive fluorohydrocarbon propellant with carbon dioxide. The same advantageous corrosion-resisting properties may be achieved where nitrous oxideis employed as a propellant assistant in lieu of to be dispensed therefrom and also a given quantity of 10 carbondi xide', solubility'does f'notseemito water together with the bicarbonate and acidin dry form The preferred procedure, in some eases todissolve. the bicarbonate in a portion of the water which'is to beused in making p s m sit qn and t n ad the acid be as great. Nevertheless, the use of nitjrous oxide asa propellant. assistantjnay be desirable insome instances. Similarly, the invention is ap pli cable to compositions .wherein nitrous oxide and/or carbon dioxide are used in tablet form, for example in the case .of citric ,acid. as t p pel t, n 110 fl qr hyg dqa (FIEOIIQ In other instances,;both the citric acid and the bicarbonatef have been predissolvedinseparate" portionsofthe water which is to be employed. The-container is promptly.

Genetron, isotron) is employed. For'ex'ample, it is applicable to edible compositions of the kind which employ a propellant comprising 85% nitrous oxide and 15% sealed after the above-named components are addedfand carbon dioxide.

liquefied Freon is forced into the'sealed container under hydraulic pressure through the valve. .When both: the bicarbonate and acid are added in solution form, the" bicarbonate solution is .fed into the sealed can through the valve just prior to Freon.

may be used so long as they are compatible with.,the.f other ingredients and will not adversely alfect persons or objectsto be subjected thereto.. Accordingly, acids'like acetic, citraconic,.itaconic, ,tartaric, malic, maleic, fumari c,

succinic, and adlpic, maybe used in specific, instancesl The invention is useful in all the various t ypesoffproi pellant compositions now in commerciallfuse such as insecticides, perfurnants, paints eleaners plasticsgartificial snow. producing compositions, deodoran'ts," hair 'f: ;-r"

For pressure in the range of to 70 pounds per squar inch, theamount of bicarbonate .used.willusuallytbein the range ofabout L to mgwmr ajstoichiometric,quahg. tity of the acid or a. small excess thereof 'to insur. utiliZa-j. tion of all thebicarbonate. Howeventhere is" no criticall limit and any desired amountfof,theseingredlents-may; be, used depending. upon the pressure desired in'fthe con-2 tainer, a great amount giving a higher pressure and a small amount a lower pressure. An aerosolpackage asgenerally:describedrabove, and as in each ,of the following. specific examples, has".su'r prising. propertiesuof corrosion resistance .throughoutja long peniodof shelf-life, .a minimun iiof 1 5 tQIZOmo'nth This is ,true ev enfthro'u gh hyaiblyzable'eompdne I as methylene chloride,"i Freoiil 1, "etc. are; erriployedffin the package alongwitli the substantial amouatar'war I lt h as been observed in most casesthatsuch compost s, when placed in commercial grade tin-lined cansgdeveldp on the interior of the can'fa characteristic gray film. Al thoughthe film develops 'within a short time'fafter "th'j composition is packaged, it is substantially identical'to its." appearance after the package has beenstored for a year or more. Except for the form'tion of the gray film,'the interior of the metal container in which the composition is'stored is not otherwise altered and the corrosion and pin-holding of the metal, co'ntain'erfwhichv ordinarilyoccurs when hydrolyzable 'componentsare' employed. with water. does not develop. This advantageousfeaturejof thepresent invention may be also achieved in 'aer'osol'f compositionsf in which certain of the reaction products, of the. bicarbonate andcitric acid, (or other namedsaltsu and acid), are themselves added to they water-containing composition which is thereafter placed in tin-lined metal"; containers. More precisely, itis only necessary, for. ex, v7

' nq si. as 1 1 1, a d... o e an 1h? n nfi q t ipw The following e ample; will furtlier"illustrate the in;

vention in relation to s o'rpe offt he various types "of products which are in commercial'us'el 1: 4 if Erizmlel A preferred acid is .citric acid, althoughother acids p A' deo dor'ant "composition in accordance: with this in-' vention'has' the following formula, by "weight:

,The composition is. prepaied by placingin the contairier to. be .used, equipped with the usual dispensing ve t p op l n yco t e l y o s p c y J 'alcohol, methylene chloride and waterl. Just before the container issealed, dry tablets of citric acid andbicarbonate of soda are dropped into the, eontainen The container is then promptly sealed and the Freon charged hrough the valve ,mechanism undefhydraulic into. it t the blets. haye hadv time to dissolve th li id 1 na tt ani v ah aafia s emo r lee-weir .pr pared usin g the same procedureexcfept, 1Z5 "ts pf fthe 28 parts br; ae'r.wer e used'tof bonate. The, citric'j facid 'was in '1 pelletfand in others the citric acid aisseiv d fn the i'einaihing 1 5,5 parts of. Water. 1 The compositionresults in apressure of pounds per square inch at F. and loses only aboutIO pounds p as" 'th'e dispensin g. of the liquid" proceeds 'to completion.

n1 casesaddedfas vThe conta ners: mployed in malt'iirg;upitheseaerosol compositions were conventional six ounce. tin-lined 7 aerosolicontainers. A, number of samples were opened i than ja ye r storagegandgthe interior of e hi dt era film descr bsd l avi at;

s r mm g ine'h Equal y gcpd. ,rc ults. .vvere bt in properties to a useful degree. The carbon dioxide, when sp ray1ng pressure} Example 2 An artificial snow producing composition in accordance with the present invention has the following composition, by weight:

Powdered mixture of sodium bicarbonate and citric acid in stoichiometric amounts V Total 100.0

In this case the bicarbonate and acid were added as a powdered mixture just prior to the hermetical sealing of the container and the charging of it with the Freon. It gave a pressure in the container of 60 pounds per square inch at 70 F. which dropped a maximum of only pounds per square inch during dispensing of the contents.

By changing the composition to provide 34.7% water instead of 37%, and 5% mixture instead of 2.5%, the pressure was increased to 65 pounds per square inch at 70 F. and it was possible to completely dispense the contents of the container.

'The above-described snow composition was placed in conventional Crown cans having a tin lining, and after being stored for more than a year no corrosion was observable on the interior of the can. In this instance also, the characteristic gray film appeared on the interior of the can.

Other samples of this artificial snow composition were produced employing the components in the same proportions described above, except that in place of the powdered mixture of sodium bicarbonate and citric acid, the reaction products themselves of this salt and acid were employed, the carbon dioxide being introduced as a propellant assistant from an external supply of carbon dioxide gas. The composition made up in this manner exhibited equally satisfactory corrosion resistance and performance characteristics.

Example 3 An insecticidal composition in accordance with this invention which is particularly effective against flies comprises the following ingredients in the proportions indicated by weight:

The composition was prepared similarly to the previous one mentioned in which all but the last three ingredients listed were first placed in the dispensing container, then the potassium bicarbonate and citric acid in dry form. The container was then promptly sealed and the Freon injected into the container through the dispensing valve under hydraulic pressure.

The containers employed were conventional six-ounce cans having a tin lining. The samples were opened after more than a years storage, and no corrosion had occurred; the formation of a gray film on the interior sur-- face of the can was observed in all samples.

Further insecticide compositions were made employing the same ingredients as described above, except that the potassium bicarbonate was eliminated and 3% sodium citrate was employed in place of the potassium bicarbonate. Carbon dioxide as a propellant assistant was introduced from an external source of carbon dioxide gas to provide a pressure of about 53 pounds per square inch. Other samples were prepared as described immediately above (using the sodium citrate), except the carbon dioxide was not employed. Further samples were prepared in the same manner as described immediately above, except that nitrous oxide was used as a propellant assistant, this being introduced from an external supply of the gas to provide a pressure of about 66 pounds per square inch.

All samples were placed in both six-ounce and fourounce conventional containers having a tin lining, and were subjected to accelerated aging tests. At the end of a period of time corresponding to the conventional shelflife of such products, representative samples were inspected and no corrosion was observed. In each instance the interior of the cans displayed a gray film.

Regarding all of the foregoing examples given above, it was observed that in addition to the density of the water and organic liquid phase being substantially the same, the pH value of the compositions when initially made up was in the vicinity of neutrality, but slightly on the acid side, and that in older compositions made according to the invention, the pH value changed towards neutral over a period of time. For example, samples showed a pH value of about 5 when first prepared, and after storage for more than a year indicated a pH of 6.5. Consequently, the pH value of the described compositions is in the area where attack on the tin lining of the cans would be minimized, and in addition to this, the compositions have the characteristic of very early forming a gray film on the tin-plated interior of the cans which does not change in character over the course of long storage.

It will be appreciated that the Well-known principles of preparing aerosol compositions are applicable to the present invention. For example, the specific examples given herein are for the purpose of illustrating the invention, and it will be appreciated that the precise percentages of components which are mentioned may be varied as usual in the formulation of aerosol products. The essential feature of the present invention resides in the combination of ingredients which make it possible to substitute a substantial amount of water for more expensive organic compounds previously used, in compositions wherein hydrolyzable components are employed. This corrosion inhibition follows from the employment of citrate and acid ions (as well as the ions and acids referred to in the specification), in combination with a tin-lined metal container. The examples disclose compositions employing about 27 to 37% water, but more or less may be employed. The advantages of the invention, it will be evident, begin at the point where any water is employed with hydrolyzable components, and the advantages in most all instances are proportionate to the amount of water that can be substituted for the more costly organic materials. In certain types of compositions, for example, window cleaners, a very substantial proportion of water may be employed along with components such as methylene chloride and trichloromonofiuormethane (propellant 11) which could not be previously employed in such compositions when packaged in metal containers. In compositions of this nature up to 75% or more water is ernployed, so that the invention, as summarized immediately above may be successfully employed in packaging aerosol compositions containing from 1% or less of water up to 75% or more. The invention is also applicable to foam type aerosol products in which the proportion of fluorinated hydrocarbon propellant is relatively low, for example only 5 to 8 or 8 to 10%. In

such products, employment .of the present invention en-' ables reducing. the amount of. fiuorinated hydrocarbon. propellant down to about-2% thus efiecting a considerable saving'even in; products of this nature." In other prod- I ucts more. than 50%; fiuorinated hydrocarbon propellant;

hasxbe'nused' and the'present: invention effects substantialzfsaving even when used' to cutv thisfto about. 50%.

In some products which normally contain a large amount of water, for example window cleaning compositions and the like, having up .to.9.5%- water, the invention is particularly applicable, especially with respect to'the fea-' ture which permits employing useful amounts of carbon dioxide as a propellant or propellant assistant. .Where an acid and carbonate are employed to produce. the prop pellant assistant in situ; as well as provide the, anticorrosion' action, the. combined amount of acid and carbonate'rnay range from .5 "to 2.0%, depending upon the pressure desired. The larger amounts may be used where high-pressures are desired, for example in some commercial applications where large, strong containers are employed. As a guide in applying the invention to.

such various compositions as described inthe foregoing parts of the specification, it isflpreferred to use sutficient;

weakly ionized acid, suchas citric, to provide the composition with any initial pH value of about 5 while there is also present the ions provided'by sodium citrate (on ions provided by. arelatively highly ionized salt .of the corresponding acid. selected for use). In certain products, such as, for example, highly carbonated ones, and/ or those containing edible acids as phosphoric, the initial pH value may be adjusted in the range 01Ev 3.5 to 4.5,, but preferably'atv thehigher: figurein such cases.

The usual'practiceshin connection with theme of.

emulsifiers are applicable to}- the compositions v described herein. .Forj example',..the emulsification ofl water and organic: liquid: phases, may be greatly facilitated by employing emulsifiers sold under-the trade name Pluronic L-64, Tween-20, Span-20, as well as others which,

are presently employed, .For example, the; compositions described in; Example 3 were made, using Tween-20 as the emulsifier. .However, as explained above, the usual practices. in connection with the use of emulsifiers are equally applicable here. I claim:

1'; A'pressurized selfedispensingpackage comprising an iron container having tin on its. interior, and a composi tiorr therein comprising water, at least;-one organic ma,-. terial' which; ordinarily produces corrosion selected from:

the group consisting" ofalcohols5 and halogenated hydro- 8 carbons which ordinarily produce corrosion due to bydrolysis, and an, alkali metal salt oi an aliphatic hydroxy carboztylicf acidih'avi g a. y y 'fouaj the lplh' ip sition to the carboxylic group inan" amount sufiic'ientto inhibit corrosion by said corrosion causing material.

2. A. pressurized self-dispensing package fasclaimed in claim 1 in which'one' of the materials which ordinarily causes corrosion due to hydrolysis is a, halogenated hydrocarbonpropellant.

-3.A'pressuri2ed' self-dispensing package, as claimed. in claini 2 in which the said: propellantis a fluorinated,

hydrocarbon.

4. A'pressurized self-dispensing package ,as claimed in claim 3 which also contains gaseous carbon dio'xi' e, whereby complete emptying of the package may be accomplished with less fiuo rinated hydrocarbon propellaint thanwould otherwise be required.-

5.. A pressurized self-dispensing package ,as-claimed. in

claim 4 in which the alkali-metal salt isa citrate.

6.. A pressurized self-dispensing package as claimed. in claim 5 in which the alkali-metal citrate and the gaseous carbon dioxide are formed within the. package by the reaction of an alkali-metal carbonate and citric acid. 1']. A pressurized self-dispensing package as claimed inclaim 6 in; which the alkali-metal carbonate is sodium.

bicarbonate.

8. A pressurized self-dispensing package as claimed. in claim 3 which, in addition to said fiuorinated hydrocarbon propellant, also containsat least one organic solvent which ordinarily causes corrosion due 'to hydrolysis. 91A pressurized self-dispensing package as claimedin claim 8 in which one of said'organic solvents ispmethylene chloride.

10. A pressurized self-dispensing package as claimed.

in'claim 9 inzwhich' the organic solvent phase and/the aqueous phase are of substantially-the.samedensity. l

. Reterencescited in the, file of this patent- 

1. A PRESSURIZED SELF-DISPENSING PACKAGE COMPRISING AN IRON CONTAINER HAVING TIN ON ITS INTERIOR, AND A COMPOSITION THEREIN COMPRISING WATER, AT LEAST ONE ORGANIC MATERIAL WHICH ORDINARILY PRODUCES CORROSION SELECTED FROM THE GROUP CONSISTING OF ALCOHOLS AND HALOGENATED HYDROCARBONS WHICH ORDINARILY PRODUCE CORROSION DUE TO HYDROLYSIS, AND AN ALKALI METAL SALT OF AN ALIPHATIC HYDROXY CARBOXYLIC ACID HAVING A HYDROXY GROUP IN TE ALPHA POSITION TO THE CARBOXYLIC GROUP IN AN AMOUNT SUFFICIENT TO INHIBIT CORROSION BY SAID CORROSION CAUSING MATERIAL. 